1. Field of the Invention
The present invention relates to a protection cover for a thermal printhead. The present invention also relates to a thermal printhead utilizing such a protection cover.
2. Description of the Related Art
A conventional thermal printhead used in combination with a protection cover is disclosed in JP-A-8(1996)-258309 for example. The conventional printhead includes an elongated head substrate provided with a heating resistor, and a circuit board formed with a predetermined wiring pattern. The circuit board carries a connector electrically connected to the wiring pattern. The head substrate and the circuit board are both mounted on a heat sink. The conventional printhead also includes a protection cover made of synthetic resin. The protection cover is provided for covering the circuit board and part of the head substrate.
The conventional protection cover is made by molding a thermosetting resin such as epoxy. In this way, however, the resulting protection cover tends to deform, for instance, when it cools after being removed from the dies. Thus, it can happen that the finally obtained protection cover may unduly warp downward, with its respective ends raised above its longitudinal center.
Disadvantageously, when the deformed protection cover is used for the conventional thermal printhead, the platen roller may fail to uniformly press a recording paper sheet or transfer ink ribbon onto the protection cover. Consequently, the recording paper sheet and/or the ink ribbon may be unduly strongly pressed onto one (or both) of the longitudinal ends of the protection cover, and therefore torn or wrinkled through the uneven contact with the protection cover.
The above problem may be eliminated by causing the resulting protection cover to have an upwardly warping form, i.e., with its longitudinal center raised above its respective ends. With such an arrangement, the recording paper sheet and/or ink ribbon are relatively strongly pressed onto the central portion of the protection cover only. Thus, the recording paper sheet and/or ink ribbon will not be torn nor wrinkled.
Conventionally, the convex protection cover is formed by using a particularly configured die whose inner surface (shape-defining surface) is upwardly warped in correspondence to the protection cover to be produced. However, it is often quite difficult to process a die to have such a particularly configured inner surface, or even impossible to do so without employing a special processing technique. Thus, forming the upwardly warped protection cover is often time-consuming and/or troublesome, thereby leading to an unduly large cost increase.